Control unit for intermittent suction system

ABSTRACT

An intermittent suction regulator is disclosed operating from a vacuum system and is used to provide a plurality of pneumatic output signals to a positive pulse device for returning fluids removed from a patient during drainage thereof to clear the removal passageways. The suction regulator or control unit provides two (2) timed output signals, from one (1) intermittent vacuum to atmospheric pressure input. One output signal continually switches from a regulated vacuum signal to an atmospheric pressure signal while the other output signal switches from providing an unregulated vacuum signal to an atmospheric pressure signal. The signals are timed such that both are initially set to provide vacuum signals simultaneously, however there is a predetermined time delay between the time the regulated vacuum output signal switches from vacuum to atmospheric and when the unregulated vacuum output signal switches from vacuum to atmospheric. Both output signals, however, again switch back to their vacuum signals simultaneously after a predetermined cycle time.

BACKGROUND OF THE INVENTION

This invention relates to a pneumatic timing device and, moreparticularly, to an intermittent suction regulator for providing variouspulsed, timed signals to operate a positive pulse suction device.

Intermittent suction devices are used regularly to remove fluids frompatients cavities, such as the stomach, and typically are utilizedpost-operatively to remove those fluids. Such devices operate typicallyfrom a main source of vacuum that is available in hospital recoveryrooms by means of central piping systems.

In non-intermittent suction units, the hospital vacuum system withdrawsthe fluids continuously into some receiver and automaticallydiscontinues the withdrawing cycle only when the collection container isfull or hospital personnel disable the system.

With intermittent suction, the continuous withdrawing of fluids isintermittently, at timed intervals discontinued. In some units, thevacuum to the tubing withdrawing the fluids is cycled to atmosphericpressure so that a portion of the fluid moves backwardly toward thepatient in order to clear obstructions in the line or to move thecatheter away from the wall of the stomach. One difficulty with suchsystems is that the back flush is carried out to some extent bygravitational forces and therefore the collection container was placedhigher than the patient, often incorporated into the timing apparatusitself on the hospital wall at the height of the receptacle providingthe vacuum. In addition, gravity force often was not effective in thatthe tubing carrying fluid from the patient seldom contained a solid lineof liquid but more often carried pockets of gas. A typical device of thetype that returned the line withdrawing fluids to atmospheric pressureis shown and described in U.S. Pat. No. 3,659,605 of Ulrich Sielaff.

In an effort to correct some of the problems, positive pulse deviceshave been proposed and which send a positive quantity of fluidpreviously withdrawn from the patient, backwards toward the patient toclean the passageways. One of such devices is shown and described inU.S. Pat. No. 4,315,506 to Kayser et al.

While the normal suction/atmospheric cycle is sufficient to operate adevice such as that of Kayser et al., it is advantageous to use othercontrol systems, that provide more than one vacuum/atmospheric signal tothe positive pulse suction device. By having more than one output signalfrom an intermittent suction regulator, one vacuum signal may beregulated in accordance with the desired vacuum to be applied to thepatients cavity while the other vacuum signal may be unaffected bychanges in the suction level to the patient and thus can independentlycontrol the timing of the positive pulse device. In addition, though theuse of a control unit or suction regulator having two (2) outputsignals, one signal can be delayed or altered with respect to time withreference to the other signal.

BRIEF SUMMARY OF THE INVENTION

The present intermittent suction regulator or control unit thus may bepowered entirely by the normal central vacuum system in a hospital andyet provides two (2) output signals, one of which is a regulated vacuumsignal that continues to switch between regulated vacuum and atmosphericpressure similar to that of the Sielaff U.S. Pat. No. 3,659,605. Thissignal can be applied to the patient's cavity since the regulator can beset to the desired level of vacuum to be applied to the patient. Asecond signal is provided by the intermittent suction regulator that maybe an unregulated vacuum and which cycles in synchronization with theregulated vacuum signal. The latter signal, however, is further providedwith a unique pause valve means that introduces a predetermined timedelay in its output switching to atmospheric upon it's input sensing achange from vacuum to atmospheric pressure Thus, both vacuum signals areturned on simultaneously, however, when the first output deliveringregulated vacuum to the patient is switched to atmospheric pressure, theother output signal representing unregulated vacuum is delayedmomentarily before switching to its atmospheric pressure cycle. Thus,the vacuum from the first output signal is cycled to the patient and isregulated while the other output provides a vacuum signal that is alsocycled with a time delay during one cycle change and which is used tooperate the positive pulse suction device, thus, the latter signal canbe used to operate the device while being isolated from the actualvacuum signal seen by the patient.

BRIEF DESCRIPTION OF THE DRAWINGS

The intermittent suction control unit is illustrated in the accompanyingdrawings which show the preferred embodiment of the inventionincorporating the features and advantages described.

FIG. 1 is a flow diagram showing the control unit of the presentinvention installed to operate a positive pulse device attached to acatheter;

FIG. 2 is a flow diagram of the intermittent suction mechanism used withthe present invention;

FIG. 3A is a cross-sectional view of the pause valve made in accordancewith the present invention and used in the control unit of FIG. 2;

FIG. 3B is a cross-sectional view of the pause valve of FIG. 3A in itsalternate position;

FIG. 4A is a cross-sectional view of a positive pulse device that isoperable by means of the intermittent suction control unit of thepresent invention and shown in its VACUUM OFF mode;

FIG. 4B is a cross-sectional view of the positive pulse device, of FIG.4A shown in the VACUUM APPLIED mode;

FIG. 4C is a cross-sectional view of the positive pulse device of FIG.4A shown in the VACUUM ON mode; and

FIG. 4D is a cross-sectional view of the positive pulse device of FIG.4A shown in the REFLUX mode.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, there is shown a flow diagram of a positivepulse suction system and having as a component; the new pause valve andintermittent suction control unit for removal of fluids from a patient.

A vacuum source 10 provides a regulated vacuum for operation of thesuction system. Vacuum sources are relatively common in hospitals andprovide a source of vacuum in certain individual hospital rooms from acentral vacuum pumping system. The vacuum of such hospital systemstypically may range within 300-600 mm Hg.

An intermittent suction control unit 12 of the present invention isconnected to the vacuum source 10 by suitable connection means such aspiping 14. The control unit 12 used in the present invention has oneoutput shown as a regulated vacuum line 16 that leads to a collectioncontainer 18 and which receives the fluids drained from the patient.Control unit 12 has a second output shown as vacuum signal line 20 thatgoes directly into the positive pulse device 22 as will be explained.

Also connecting into the positive pulse device 22 is the regulatedvacuum line 24 from container 18. A catheter 26 which is attached to thepositive pulse device 22 and which is placed in the patient such thatthe open catheter end 28 reaches the fluids desired to be withdrawn. Thepassageways for fluid, regulated vacuum line 24 as well as vacuum signalline 20 and regulated vacuum line 16 may be standard relatively flexiblemedical tubing.

Turning now to FIG. 2, there is shown a flow diagram of the intermittentsuction control unit 12 made in accordance with the present invention.The overall purpose of control unit 12 is to provide two (2) separatesignal outputs, one being a regulated vacuum signal for ultimate usewith the patient and the second signal, that need not be regulated actsas a vacuum signal for operating the positive pulse device. The presentcontrol unit 12 is pneumatically operated, however, the signals could beachieved by electronic switching or other means.

One of the important improvements between control unit 12 and theintermittent suction unit of the aforementioned Sielaff patent is thatcontrol unit 12 provides two (2) vacuum output signals at differenttiming cycles. In its operation, control unit 12 simultaneously suppliesvacuum to two (2) outputs, one regulated and one that need not beregulated. During suction at the patient, control unit 12 simultaneouslysupplies vacuum at both outputs and after the duration of the suctioncycle, control unit 12 returns the regulated vacuum line, to thepatient, to atmospheric pressure. After a predetermined short timeinterval the other vacuum output signal is returned to atmosphericpressure.

In FIG. 2, the vacuum source 10 provides the vacuum to control unit 12as described previously with respect to FIG. 1. That source of vacuum isinitially controlled by an "on-off" switch 30 which merely shuts off thevacuum from vacuum source 10 when the unit is not in use. A intermittentdevice 32 thereafter is controlled by the vacuum and may be of the samedesign as shown in the aforemention Sielaff U.S. Pat. No. 3,659,605.Intermittent device 32 includes an atmospheric vent 34 by which thefurther lines withdrawing fluids from the patient are intermittentlyvented to atmospheric pressure.

Tracing now, the source of vacuum that ultimately reaches the patient,the intermittent vacuum/atmospheric pressure signal from intermittentdevice 32 proceeds via passages 36 and 38 to a vacuum regulator 40 wherethe doctor, or other qualified personnel, actually sets the maximumlevel of vacuum that the patient can experience. The vacuum regulator 40is conventional and thereafter the regulated vacuum proceeds by passage42 to connect with regulated vacuum line 16 to collection container 18(FIG. 1). A vacuum gauge 44 is in the passage 42 so that the doctor canverify and continually monitor that the regulated vacuum from controlunit 12 is at the desired set point.

Returning to the intermittent device 32, the same intermittentvacuum/atmospheric pressure signal proceeds via passages 36 and 46 to apause valve 48 where a predetermined time delay is created between thetime that the signal from intermittent device 32 goes from vacuum toatmospheric pressure and the time that signal from the output of pausevalve 48 to passage 50 goes from vacuum to atmospheric pressure, as willbe latter explained. The passage 50 connects to vacuum signal line 20 ofFIG. 1 and is used to control the positive pulse device 22. A liquidsafety trap 51 is provided in passage 50 in order to prevent liquid fromreturning and entering pause valve 48.

The pause valve 48 is made and operated in accordance with the presentinvention.

Turning now to FIGS. 3A and 3B, there is shown cross-sectional views ofthe pause valve 48. Pause valve 48 comprises a housing 52, preferably ofa plastic material having an inlet 54 which connects to passage 46 ofFIG. 2 which is the intermittent vacuum/atmospheric pressure signal fromthe intermittent device (FIG. 2) and an outlet 56 which, in turn,connects to passage 50 of FIG. 2 and thereafter to the positive pulsedevice 22 (FIG. 1) and provides the vacuum signal therefore. Withinhousing 52 of pause valve 48 is a moveable valve member 58 and a valveseat 60. The moveable valve member 58 is retained within housing 52 bythree diaphragms 62, 64 and 66 and which form various chambers in orderthat various levels of vacuum and/or atmospheric pressure influence themovement and position of moveable valve member 58. The diaphragms 62, 64and 66 specifically divide the interior of the pause valve 48 into pilotchambers 68, 70 and main chambers 72 and 74.

Moveable valve member 58 additionally has a resilient pad 75 that sealsagainst valve seat 60 when in the valve closed position of FIG. 3B. Asshown in FIG. 3A, the moveable valve member 58 is in the valve openposition and resilient pad 75 is not seated against valve seat 60.

Various passages are formed in housing 52, passage 76 communicatesdirectly between inlet 54 and pilot chamber 70 while passage 78 is alonger passage than passage 76 and provides communication between inlet54 and main chamber 74, the purpose of passage 78 being longer or havingmore resistance than passage 76 will become clear.

The pilot chambers 68 and 70 also are in communication between eachother through a fixed orifice 80 which extends between pilot chamber 70and reservoir 82 and by passage 84 between reservoir 82 and the otherpilot chamber 68, otherwise pilot chambers 68 and 70 are isolated fromeach other by diaphragm 64. A spring 86 biases the moveable valve member58 toward its valve open position as shown in FIG. 3A.

Taking now the operation of the pause valve 48, it should be remindedthat the purpose thereof is to introduce a short delay between the timethat the vacuum signal at its inlet 54 goes from vacuum to atmosphericpressure and the time that the vacuum signal at its outlet 56 goes toatmospheric pressure. As seen in FIG. 2, the delay occurs such that whenthe vacuum in passage 36 switches from vacuum to atmospheric pressure bythe intermittent device 32, the regulated vacuum in passage 42 leadingto the patient immediately also switches from vacuum to atmosphericwhile the signal in passage 50 is delayed slightly before it switchesfrom vacuum to atmospheric pressure. Both signals, that in passage 36and 42 are, however, controlled by intermittent device 32.

Returning to FIGS. 3A and 3B, the cycle can be commenced with allchambers, that is pilot chambers 68, 70 and main chambers 72 and 74 atatmospheric pressure and the valve is in the valve open position of FIG.3A. As vacuum is applied to inlet 54 when the intermittent device 32commences its vacuum or suction cycle, the vacuum immediately reachespilot chamber 70, thereby reinforcing the bias of spring 86 andretaining the moveable valve member 58 in the position shown in FIG. 3A.The vacuum also communicates through passage 78 to draw a vacuum in mainchambers 74 and 72. At this point, therefore, vacuum is drawn at outlet56 and pilot chamber 70 as well as main chambers 74 and 72 so that allchambers except pilot chamber 68 are at the high vacuum seen at theinlet 54. As time passes, the reservoir 82 is slowly evacuated throughfixed orifice 80 such that over a predetermined time period, pilotchamber 68 also reaches high vacuum. At this point, all of the chambers68, 70, 72 and 74 are at high vacuum.

As the intermittent device 32 switches to its atmospheric pressure mode,the pressure at inlet 54 immediately goes to atmospheric pressure andatmospheric pressure is simultaneously communicated to pilot chamber 70through passage 76. Since the other chambers effecting surfaces of themoveable valve member 58 are balanced at high vacuum, the atmosphericpressure in pilot chamber 70 overcomes the force of spring 86 and movesthe pause valve 48 to its position shown in FIG. 3B causing resilientpad 75 to close against valve seat 60. Since the passage 78 isrelatively long and restricted, the valve seat 60 is closed by resilientpad 75 before atmospheric pressure can travel through passage 78 toreach main chamber 74. Thus, at this point in time, only the pilotchamber 70 and passages 76 and 78 are at atmospheric pressure while mainchambers 72, 74 and the reservoir 82 are still at high vacuum.

Reservoir 82, however, slowly returns to atmospheric pressure bydissipation of its vacuum through atmospheric pressure entering throughfixed orifice 80. As reservoir 82 returns to atmospheric pressure, sodoes pilot chamber 68. When pilot chamber 68 reaches atmosphericpressure, the pressure related forces on moveable valve member 58 becomeequal since both pilot chambers are at atmospheric pressure and theareas through which that atmospheric pressure acts upon moveable valvemember 58 are equal. The main chamber 72 and 74 are both still at highvacuum and the respective areas acting upon moveable valve member 58 arealso equal, thus the only additional force acting upon moveable valvemember 58 is the bias of spring 86 which is the resultant force andwhich moves the moveable valve member 58 back to its valve positionposition shown in FIG. 3A.

As the moveable valve member 58 moves to the FIG. 3A position, thepassage through valve seat 60 also opens such that all chambers 68, 70,72 and 74 are returned to atmospheric pressure and therefore the outlet56 returns to atmospheric pressure. Thus a time delay is introducedbetween the time the inlet 54 is vented to atmospheric pressure and thetime that atmospheric pressure appears as a signal at outlet 56.

Obviously, the actual pause time is a matter of design and depends uponthe characteristics of spring 86, the volume of reservoir 82, the vacuumlevels applied and the size of orifice 80.

Thus, in accordance with the present invention, a pause valve isdescribed and which is usable in a unique intermittent suction controlunit 12 used to control a positive pulse device by providing a pluralityof vacuum and atmospheric pressure signals at predetermined timedintervals.

Turning now to FIGS. 4A-4D, there is shown a positive pulse device 22that can be used with the signals of control unit 12 to withdraw fluidsfrom a patient shown in its four (4) basic positions respectively, theVACUUM OFF, the VACUUM APPLIED mode, the VACUUM ON mode, and the REFLUXmode.

Taking FIG. 4A first, the positive pulse device 22 comprising a housing88 which is conveniently made up of lower housing 90 and upper housing92 which are joined together as will be explained. Housing 88 has aninlet 94 which is connected to the collection chamber 18 (see FIG. 1)and therefore is connected to the source of regulated vacuum. An outlet96 is also formed in housing 88 and is adapted to be connected directlyor adjacent to a patient catheter. A valve means is interposed betweeninlet 94 and outlet 96 and is formed by valve seat 98 and moveable valvemember 100 that moves into engagement with valve seat 98 or awaytherefrom to control the flow between inlet 94 and outlet 96. Moveablevalve member 100 has a truncated conical shape surface 102 that mateswith valve seat 98 and which also forms an annular ridge 104 facingupwardly away from valve seat 98.

Moveable valve member 100 includes a valve extension 106 that dependsupwardly and which is sonic welded to the lower part of moveable valvemember. A spring bias is provided by a small spring 108 and which actsto bias the moveable valve member 100 toward its closed position againstvalve seat 98. This spring bias is very small, however, and is createdby the preload effected by installing small spring 108 with lower end ofsmall spring 108 seating on inner ledge 110 formed in the valveextension 106 and its upper end held by the lower end of moveable cap112. Moveable cap 112, in turn, is biased toward valve extension 106 bymedium spring 114 which acts against a flange 114 of moveable cap 112having its other end seated against the top of housing 88. The moveablecap 112 is contained within a keeper 116 which retains the moveable cap112 in position and limits its downward movement by an inner ledge 117.As noted in FIG. 4A, in the VACUUM OFF mode, the moveable cap 112 at itslowermost position does not directly touch the upper end of valveextension 106 in its lowermost position. Instead a gap 118 of about 0.04inches is retained between the bottom of moveable cap 112 when it is inits lowermost position and the top of valve extension 106 when it is inits lowermost position. As will become clear, the spring constant orbias exerted by medium spring 114 is higher than that of small spring108.

Surrounding moveable valve member 100 is an annular piston 120 thatmoves independent of moveable valve member 100, however, in the positionof FIG. 4A, annular piston 120 directly engages the annular ridge 104 ofmoveable valve member 100 and urges the moveable valve member 100 towardits closed position by the bias of large spring 122 which isprecompressed and has its lower end held within annular groove 124 inannular piston 120 and its other end abuts against the top of housing 88and held in position by spring keeper 126. Thus, in the VACUUM OFF modeof FIG. 4A, the large spring 122 acts as an additional force inretaining the moveable valve member 100 in its closed position againstvalve seat 98.

A diaphragm 128 creates a control chamber 130 in the upper housing 92and which control chamber 130 is sealed except for control port 132which is adapted to be connected to vacuum signal line 20 (shown in FIG.1). Diaphragm 128 has its outer peripheral edge secured in housing 88 bybeing sandwiched between lower housing 90 and upper housing 92 which maybe sonic welded together. Diaphragm 128 has its inner edge sealed tomoveable valve member 100 by the connection of the valve extension 106to the lower part thereof, again which may be a sonic welded connection.Intermediate its outer periphery and its inner edge, diaphragm 128 isalso sealed to annular piston 120, which seal may be effected bycompressing the diaphragm 128 against annular piston 120 by means ofannular cap 134 which also may be sonic welded to annular piston 120.

As shown, the diaphragm 128 is a single piece of flexible material,however, it may readily be made up of two (2) separate diaphragms whilestill carrying out the purpose of forming a pair of rolling seals, thatis, an outer rolling seal at 136 and an inner rolling seal at 138. Eachof the rolling seals 136 and 138 allow independent movement of moveablevalve member 100 and annular piston 120 with respect to each other andyet retain the integrity of the control chamber 130.

Referring now to FIG. 1 as well as FIGS. 4A-4D, the operation of thepositive pulse device 22 can be readily understood. Initially, atstart-up, the positive pulse device 22 is in the position as shown inFIG. 4A. At this point in the cycle, the inlet 94, outlet 96 and thecontrol part 32 are all at atmospheric pressure. The valve means isclosed since moveable valve member 100 is in its lowermost positionsealed against valve seat 98, so there is no communication between theinlet 94 and outlet 96. The moveable valve member 100 is retained inthat position, being held there by the annular piston 120 acting againstannular ridge 104 and biased by large spring 122 and by the bias of thesmall spring 108. Both large spring 122 and small spring 108 are, ofcourse, preloaded. The catheter 26, and therefore outlet 96 may, attimes, be slightly above atmospheric pressure due to positive tissuepressure in the stomach, however any drainage that might occur due togravity or differential pressure forces is prevented by the closed valvemeans.

Taking, now, the VACUUM APPLIED mode of FIG. 4B, the FIG. 4B depicts thepositive pulse device 22 slightly after the control unit 12 has switchedfrom atmospheric pressure to vacuum mode and two (2) levels of vacuumare being applied to the positive pulse device 22. Regulated vacuum isbeing applied to the inlet 94 and vacuum that need not be regulated thepipeline vacuum level of the particular hospital system, is beingapplied to control part 132 by means of vacuum signal line 20.

Initially, as those vacuum levels are applied, the unregulated vacuum inthe control chamber 130 creates a negative resultant force on theannular piston 120 since the lower surface of annular piston 120 is ator near atmospheric pressure since outlet 96 of the positive pulsedevice 22 is at atmospheric pressure. The moveable valve member 100 isstill closed and therefore the regulated vacuum at inlet 94 does notaffect that resultant force since it cannot reach outlet 96.

Accordingly, the negative resultant force on annular piston 120 causesit to move upward away from the valve seat 98 and lifts off of itscontact with annular ridge 104 of moveable valve member 100. The springbias exerted against moveable valve member 100 by large spring 122 istherefore eliminated and the moveable valve member 120 is retained inits closed position against valve seat 98 by whatever differentialpressure forces exist and by means of the rather small bias exerted bysmall spring 108. As the annular piston 120 continues to move upward,collapsing the control chamber 130, it draws a vacuum at the outlet 96and thus on the patient through catheter 26. A reflux chamber 140beneath the diaphragm 128, is created and expands, separated, of coursefrom the unregulated vacuum in the control chamber 130. Eventually, theannular piston 120 creates a sufficient vacuum at outlet 96 toapproximately equal the regulated vacuum already applied to the inlet94, and at this point, the forces acting upon the moveable valve member100; that is, the unregulated vacuum in control chamber 130, regulatedvacuum in the inlet 94, at or near regulated vacuum in outlet 96 and thesmall bias of small spring 108 cause the moveable valve member 100 towithdrawn from the contact with valve seat 98 and cracks that valvemeans between inlet 94 and outlet 96 allowing the regulated vacuum fromregulated vacuum line 24 to reach the catheter 26. Thus the regulatedvacuum prescribed for that particular patient is applied to the patientcavity to be drained and no higher vacuum reaches the patient despitefurther travel of the annular piston 120 or moveable valve member 100.

It should be noted that the position of the positive pulse device 22shown in FIG. 4B is such that the moveable valve member 100 has merelyovercome the relatively small bias of small spring 108 and thus movementof moveable valve member 100 away from valve seat 98 closes the gap 118.The moveable valve member 100 has moved approximately 0.04 inches, awayfrom valve seat 98 sufficient to crack the valve means. Further movementaway from valve seal 98 by moveable valve member 100 is thereafterresisted by the larger bias of medium spring 114.

Although the regulated vacuum is at this time being applied to thepatient through catheter 26, both the moveable valve member 100 andannular piston 120 continue to retract away from valve seat 98, howeverboth move at approximately the some rate since both are acted upon byabout the same forces. On the annular piston 120, a differential forceis created by the difference between the unregulated vacuum in controlchamber 130 acting on the annular area of annular piston 120 and theregulated vacuum in inlet and outlets 94 and 98 acting on the annulararea of annular piston 120 in addition to the force of large spring 122.On the moveable valve member 100, a differential force is created by thedifference between the unregulated vacuum in control chamber 130 actingon the upper area of moveable valve member 100 and the force of both themedium spring 114 and the small spring 108 and the regulated vacuum inthe inlet and outlet 94 and 96 acting against the lower area of moveablevalve member 100. Eventually, both the moveable valve member 100 andannular piston 120 reach their fully retracted positions shown in FIG.4C and the valve means is fully open applying regulated vacuum to thepatient to carry out the drainage.

FIG. 4C shows the VACUUM ON mode where unregulated or full line vacuumis applied to control part 132 retaining the now collapsed controlchamber 130 at full line vacuum to hold annular piston 120 and moveablevalve member 100 in their fully retracted positions compressing largespring 122, medium spring 114 and small spring 108. Regulated vacuum iscontinuously applied to the patient from inlet 94 to outlet 96 and thusto catheter 26 and gases and other fluids can be withdrawn through thefully open valve means to be collected in collection container 18.

The positive pulse device continues in its position of FIG. 4C until thecontrol unit 12 switches to release the vacuum signal in passage 36 ofFIG. 2 to atmospheric pressure. As previously described, initially onlythe regulated vacuum in regulated vacuum lines 16 and 24 are vented toatmospheric pressure and thus the inlet 94, outlet 96 and patient viacatheter 26 are immediately vented to atmospheric pressure. After a fewseconds delay, the vacuum signal line 20 applied to control part 132 andtherefore control chamber 130 is also vented to atmospheric pressure.The control chamber 130 returns to atmospheric pressure as does thereflux chamber 140 and the inlet 94 and outlet 96; thus the combinedforces on the moveable valve member 100 and annular piston 120 by meansof the large spring 122, medium spring 114 and small spring 108 causethe moveable valve member 100 and annular piston 120 to move towardvalve seat 98. As can be noted on FIG. 4C, the length of travel of themoveable valve member 100 is relatively short compared with the strokeof annular piston 120 and thus the moveable valve member 100 quiterapidly seats against the valve seat 98 closing the valve means and thusshutting off flow between outlet 96 and inlet 94 and isolating refluxchamber 140 from inlet 94.

As shown in FIG. 4D, the valve means is closed, yet the annular piston120 still has remaining stroke and as it continues to move toward thevalve seat 98 the reflux chamber 140 is collapsed and the fluid withinreflux chamber 140 is forced backwardly out of the outlet 96 toward thecatheter 26 and the patient. Since the moveable valve member 100 isclosed, all of the fluid remaining in reflux chamber 140 is thus forcedout the outlet to clear the passageways in the catheter. As the refluxchamber 140 is completely collapsed, the annular piston 120 again seatson the annular ridge 104 of the moveable valve member 10 so that thebias of large spring 122 again acts to retain the valve means closed andthe cycle is completed, to be continuously repeated as the control unit12 continues on to further cycles.

I claim:
 1. A control unit for use with an intermittent suction devicefor withdrawing fluids from a patient cavity, said control unit havingan inlet for connecting to a source of vacuum and having first andsecond outlets,(a) means connected to the inlet for providing a signalalternating between vacuum and atmospheric pressure at predeterminedintervals, (b) first and second passage means receiving said alternatingsignal and transmitting said signal to first and second outlets, (c)means in said second passage means to delay by a predetermined amount oftime, the time between said first and second passages sensing saidsignal changing from vacuum to atmospheric pressure and the time saidchange in signal is transmitted to said second outlet.
 2. A control unitas defined in claim 1 wherein said first passage means includes aregulator to set the vacuum level of signal reaching said first outlet.3. A control unit for use with an intermittent suction device forwithdrawing fluids from a patient cavity, said control unit having aninlet for connecting to a source of vacuum and having first and secondoutlets,(a) an intermittent suction unit connected to said inlet andhaving an outlet, said intermittent suction unit adapted to provide asignal at its outlet alternating at predetermined intervals betweenvacuum and atmospheric pressure, (b) first passage means connecting saidalternating vacuum/atmospheric pressure signal from said outlet of saidintermittent suction unit to said first outlet of said control unit, (c)said first passage means having a regulator to control the level ofvacuum delivered to said first outlet, (d) second passage meansconnecting said alternating vacuum/atmospheric pressure signal from saidoutlet of said intermittent suction unit to said second outlet, (e)pause valve means in said second passage means comprising a housinghaving an inlet and an outlet, said pause valve having means to cause apredetermined delay in the time said pause valve inlet senses a changein the signal from said intermittent suction unit vacuum to atmosphericpressure and the time said pause valve outlet signal changes from vacuumto atmospheric pressure.